The present invention relates to a tubular packaging film, useful in particular as a sausage casing for scalded and cooked sausages, which is constructed of polyamide, and which has improved physical properties compared with known polyamide tubings. While the film can advantageously be used for packaging purposes, it is especially suitable for use as a crease-free and deformation-resistant sausage casing for scalded and cooked sausages.
A great number of tubular films comprising synthetic plastic materials, for example, polyester or polyamide, are known in the art. But in sausage casings, above all, stringent requirements must met with regard particularly to their suitability from a physiological point of view, their strength, and dimensional stability.
Tubular films made of a variety of synthetic materials have the drawback of reduction in strength if water is absorbed. In many cases, the packaged material contains water and gives off moisture to the adjoining packaging film. Reduction of film strength is particularly apparent in the course of scalding or cooking of tubular casings filled with sausage meat, when the film material comes into contact with hot water or steam. The strength of the film material thereby decreases sharply due to the absorption of water.
Sausages can be treated with hot steam by being suspended by a string loop in a cooking cabinet. During this process, the lower portion of the sausage casing is heavily loaded by the weight of the filled-in sausage meat. If the casing material has insufficient dimensional stability, it then expands, such that the originally cylindrical sausage turns into a deformed pearshaped product.
To compensate for this unwelcome effect, the thickness of the packaging film has hitherto been increased correspondingly or, alternatively, attempts have been made to enhance the film strength by expensive process steps during tubing manufacture.
The strength of the casing material, however, which is reduced at the cooking or scalding temperature, can only be improved by these measures to a limited extent, and thus the deformation resistance of the casing material at this temperature is therefore only slightly increased. An excessive thickness of the casing material also involves the risk that the packaging casing becomes too rigid and inelastic. The casing can then only insufficiently expand when the filling is pressed in, and after the cooking or scalding process, it does not fully conform to the shrunken contents in the cooled state, so that the product obtained is wrinkled and unattractive.